The present invention relates to the structure for securing a cylinder drive gear to the end of a cylinder shaft in the mechanism for driving a plate cylinder or the like of a printing machine or press.
A general rotary printing press has plate cylinders or blanket cylinders with their shafts supported by the frame at their both ends, and on at least one end of such shaft there is secured a cylinder drive gear which links the cylinder to the adjacent cylinders and also to the drive mechanism. Various structures are known for securing a cylinder drive gear to the end of a cylinder shaft. In a tyical example, the end of the shaft and the cylinder drive gear are tapered so that the shaft fits in the gear, and the drive gear on the tapered portion of the shaft is pressed toward the cylinder by tightening the nut on the thread which is cut on the end portion of the shaft, so that slip in the circumferential direction can be prevented by the friction and also by use of a key provided between them. In another example, the cylinder drive gear is secured to the end of the cylinder shaft with a key provided at the contact portion thereof so that slip in the circumferential direction is prevented, and also shift of the gear in the axial direction is limited by employment of a holding plate which is fixed to the end of the shaft by a bolt. These structures are disclosed in, for example, "Oyo Kikai Kogaku" Pages 124 to 127 Vol. 17, No. 6, 1976, published by K. K. Taiga Shuppan in Japan.
However, foregoing conventional structures for securing a cylinder drive gear to a cylinder shaft have the following disadvantages. In the first mentioned prior art structure, it is difficult to machine the tapered portion and keyway accurately, resulting in a high machining cost, and also it can reduce the strength of the shaft due to a cut for the keyway and also cause eccentricity of the drive gear. In the second mentioned structure, in addition to a high machining cost and reduction of the strength owing to the machining for the keyway, the drive gear is liable to vibrate due to a poor fitting accuracy between the drive gear and the shaft, resulting in a wear of the key and shaft that causes increased vibration. In order to avoid the vibration, the securing portion must be made long and the width of the frame which supports a long shaft cannot be made small.
As described above, conventional structures for securing a cylinder drive gear have such disadvantages that vibration of the gear and wear of the key and other components owing to the inertial torque when the machine stops cannot be avoided. These problems can cause failure of printing, and improvement of the mechanism has long been desired.